Process for drying pliable supports



Dec. 2, 1969 MOTOHARU KUROKI ET 3,481,046

PROCESS FOR DRYING PLIABLE SUPPORTS Filed March '7, 1968 6 O 0 Av O 6 BB 6 6 INVENTORS MOTOHARU KUROKI TOSHEHIRO KATO I 13W, $140,} ,WATTORNEYS,

United States Patent PROCESS FOR DRYING PLIABLE SUPPORTS Motoharu Kurokiand Toshihiro Kato, Kanagawa,

Japan, assignors to Fuji Shashin Film Kabushiki Kaisha, Kanagawa, JapanFiled Mar. 7, 1968, Ser. No. 711,239 Int. Cl. F26]: 13/16 US. C]. 34-103 Claims ABSTRACT OF THE DISCLOSURE Drying solvent-containing coatinglayers on a continuously moving flexible support by helically wrappingthe coated support surface about a perforated cylindrical air chamberwith the individual air jets acting as an air bearing for the supportwhile drying the coating layer.

This invention relates to a continuous process for drying continuouslymoving pliable supports effectively and economically without any contactbetween the said support and the solid surfaces during the drying step.The process of the present invention is particularly effective fordrying solvent-containing coating layers carried by the supports.

For effective drying of solvent-containing coating layers oncontinuously moving pliable supports, there has been hitherto employed adrying process in which a coated support is supported from the reverseside with respect to its coated surface by spaced supporting rollerslocated at regular intervals to define a straight, curved or undulatedpath for the travel of the support. The stream of drying air is blownperpendicularly or substantially perpendicular to the coated surface ofthe support through perforated or slit plates. In this prior process,however, it is necessary to fabricate the rollers precisely, the surfaceof the rollers is of mirror-finish and each set of rollers is alwaysadjusted to ensure balanced rotation because, the quality of thesupporting rollers has a significant influence on the quality of thedried product. In the manufacture of photosensitive material, so calledpressure fog, static fog and an abrasion or scratch are especially fataldefects on the quality of the product and are caused by fine stains onthe surface of the supporting rollers, an electrostatic phenomenon dueto contact and removal of the support from the supporting rollers andthe slip between the supporting rollers and the support, respectively.

There has also been proposed, a process in which a coated support isconveyed without any contact with solid surfaces by blowing drying andsupporting air streams onto both sides of the coated support throughperforated or slit plates under such conditions that the velocity andquantity of the air stream sustained the support in fixed position.Although all of the defects accompanying the use of the supportingrollers are avoided in this process, it is very expensive because itrequires complicated and expensive apparatus including a large capacityair source for supporting the support and with resulting expense inoperation of the apparatus.

The present invention eliminates the defects of the prior processes. Thepresent invention consists in an economical process for dryingcontinuously movable, long pliable supports in which the support is notat all in contact with a solid surface and it is unnecessary to use anysupporting air streams other than the drying air. In the process of thepresent invention, drying of the support is performed while passing thesupport through a helical path by wrapping the support to be driedhelically around a tubular air chamber with the surface of the pliablesupport to be dried facing the outside surface of the air chamber,directing air streams from the peripheral surface of the air chamber inthe form of jets to the surface 3,481,046 Patented Dec. 2, 1969 ice tobe dried and balancing the tension in the support and the wind pressureof the drying air to support the said support on an air cushion.

The-drying process of the present invention will be illustrated withreference to the accompanying drawings, in which:

FIG. 1 is a plan view of one device for a drying pliable support inaccordance with the present invention,

FIG. 2 is an enlarged plan view of the essential parts of the samedevice, and

FIG. 3 is a plan view of a combination of such devices including thedevice of FIG. 1 as applied to a single sup port.

A support 1 having a solvent-containing coating layer to be dried isconveyed by winding it'helically around an air chamber 2 and dried inthe mannersuch that the surface to be dried faces the surface of the airchamber 2. Drying air passes through an air duct 3 into the air chamber2. Blown drying air streams exit through a number of holes 4 in theperipheral surface of the air chamber 2 to float the support 1 on theperipheral surface of the air chamber 2. The support 1 is fed by meansof, e.g., suction rollers or other suitable means (not shown). Thesupport 1, after completion of drying, is withdrawn under suitabletension by means such as a dancer roller (not shown) to impart tensionto the support 1, thereby maintaining an appropriate space between thesupport 1 and the peripheral surface of the air chamber 2.

The angle of the helix of the support 1 during drying and conveying isdetermined by both the width of the support 1 and the external diameterof the helical path. The angle is selected as small as possible suchthat each turn of the support 1 does not overlap the adjacent turns andthere is, between the adjacent turns of the support 1, an aperturesuflicient to allow escape of the drying air. In the space between thesupport 1 to be dried and the peripheral surface of the air chamber 2,the static pressure of air is greater than in the circumferential gapsurrounding the support 1 and the air chamber 2 due to the resistance tothe escape of the drying air. In addition thereto, the support 1undergoes an internal pressure by the effect of the dynamic pressure ofthe drying air streams. By suitably choosing the tension applied to thesupport 1 to balance the tension and the synthetic force of the windpressure due to said drying air streams, it is possible to sustain thesupport 1 in a fixed region near the holes 4 where the drying airstreams exit to provide maximum drying effect. The components of theforce acting on the support 1, in the direction of the axis of the airchamber 2, are balanced in each portion of the support 1, so that thesupport 1 is conveyed always along a regular path without any deviationtherefrom in the direction of the axis of the air chamber 2.

The drying air is supplied to the air chamber 2 through the air duct 3after being adjusted to the conditions of temperature and humidityrequired in the drying step and purified by means at drying air sourcessuch as, e.g., blowers, filters, heaters and dehumidifiers. The air isblown through the holes 4 of the air chamber 2 at relatively largevelocity to perform effective drying, allowed to diffuse through theaperture between the helical turns of the support 1 into the drying roomand recovered by the other exhausting apparatus.

If desired, the conditions of temperature, humidity and the velocity ofair streams may be varied by dividing the air chamber longitudinallyinto sections and supplying the drying air to each section from separateair sources. Alternately, as shown in FIG. 3, a plurality of airchambers 2, 2', 2" may be provided in parallel at a proper angle as thesupport to be dried is conveyed successively thereon with supplying theair chambers 2, 2', 2" with the drying air received through air ducts 3,3 and 3", respectively.

In the device as shown in FIG. 1, the width of the support is about 1.2m., the diameter and length of the air chamber are about 3 m. and about14 m., respectively, and the angle of the helix is about 9, and theeffective length of drying is about 65 m. A support in which the othersurface had been previously coated, was coated with an X-ray sensitivephotographic emulsion and, after being gelled in the conventional mannerto effect cooling and solidification of the coating layer, Was subjectedto drying, using this apparatus at a velocity of the drying air of 25m./sec., and a tension acting on the support of 20 kg. The drying wasperformed at a rate of 30-35 g./m. min. Without any trouble, e.g.,static fog or abrasion fog, and an X-ray film of good quality wasobtained. In this case, the drying rate was substantially equal to thedrying rate of the prior processes and the capacity of the dryingchamber used was from A to /2 of that in the latter effective process.

According to the drying process of the present invention, all of thetroubles due to supporting rollers etc., are excluded because drying isperformed Without any contact with the solid surface of the support and,in addition, drying is performed economically because it is unnecessaryto use any supporting air stream other than the drying air streams.Furthermore, no supporting roller in needed in the drying step, so thatthe apparatus used is simple and adjustment and maintenance of theapparatus can be made without any difiiculty. As the tension acting onthe support during the drying step is uniform, it is unnecessary to usetension adjusting mechanisms such as torque motors common to priorprocesses in which supporting rollers are used. Moreover, it is possibleto make the apparatus compact compared with those used in the priorprocesses in the manufacture of pliable supports.

What is claimed is:

1. A process for drying continuously moving elongated pliable supportscomprising:

providing helical turns to said support with the surface of said supportto be dried interiorly thereof, and

directing drying air onto said interior helical surface to dry the samewhile supporting said helical turns on an air cushion.

2. The process of claim 1 wherein said support is provided with helicalturns and dried by wrapping the same about a peripherally perforatedcylindrical chamber carrying pressurized drying air.

3. The process of claim 2 further including balancing the tension actingon said continuously moving pliable support with the air cushion windpressure created by the pressurized drying air exiting through theperipherally perforated chamber.

References Cited UNITED STATES PATENTS 1,473,542 11/1923 Chanier et a1.34153 2,153,376 4/1939 Kline 34-153 XR 3,102,006 8/1963 Cohn et a1.34156 XR KENNETH W. SPRAGUE, Primary Examiner U.S. Cl. X.R. 34-153, 156

